Heretofore, in a suspension mounted on an automobile, one member has been connected to another member in a vertically or otherwise swingable manner with a suspension arm member interposed in between. Examples of the suspension arm member include a suspension arm mounted to a vehicle body or an axle by a ball joint, and a stabilizer link connecting a strut and a stabilizer. Such a suspension arm member is required to have strength or rigidity, and thus, a suspension arm member made of iron is generally used. A typical stabilizer link is heavier in weight due to its support bar made of steel, as compared to a member made of a resin or a member made of aluminum.
Recently, in the field of automobiles, there has been a growing demand for an improvement in fuel economy because of a steep rise in crude oil and gasoline prices or the like, and there has been a demand for a weight reduction of the vehicle body for purposes of the improvement in the fuel economy. A plastic pendulum support disclosed in Patent Literature 1, for example, is known as the suspension arm member whose weight is reduced in order to reduce the weight of the vehicle body.
The plastic pendulum support (or the suspension arm member) disclosed in Patent Literature 1 has eight intermediate chambers in total by forming four longitudinally-elongate intermediate chambers in front and rear lateral sides, respectively, of a base body made of plastic.
The intermediate chambers include a pair of front lateral central intermediate chambers disposed in a central lower side of the front lateral side of the plastic pendulum support, a pair of front lateral outside intermediate chambers disposed at left and right outside upper symmetrical positions, respectively, with respect to the pair of front lateral central intermediate chambers, a pair of rear lateral upper central intermediate chambers disposed in a central upper side of the rear lateral side, and a pair of rear lateral outside upper intermediate chambers disposed at left and right outside lower symmetrical positions, respectively, with respect to the pair of rear lateral upper central intermediate chambers.
In the plastic pendulum support, the four longitudinally-elongate intermediate chambers are formed in the front and rear lateral sides, respectively, in an S-shape as seen in a vertical sectional view in a widthwise direction, thereby improving cross-sectional secondary moment and load resistance capability of the entire construction.